difference between history plugin and state history plugin

Question

What I know is,

• history_plugin : plugins that enable store sort of historical data like action traces, transaction traces.

• history_api_plugin : plugins that enable to use /history/* APIs.

So, state_history_plugin was introduced at v1.5.0, and this can be configured at config.ini like

• plugin = eosio::state_history_plugin
• trace-history = false
• ... ETC ...

Also, I found this (https://github.com/acoutts/EOS-state-history-API) while reading this post (https://medium.com/@eos42/scalable-full-history-nodes-b4eccf113d57). But I think this repo is just for mongo db plugin.

So, my question is...

1. What is difference between history and state history? and how can query state_history_plugin data?
2. Is there any state_history_api_plugin for RPC? (like /v1/state_history/get_actions)

Answer 1

I asked my friend Andrew Coutts this question on your behalf, and he said:

So the state history plugin is just a piece of the equation.

• The history plugin exposes the RPC API that we're all familiar with.
• The state history plugin saves state data to a new flat file format that’s designed to be read from external components and is faster to rebuild than replaying the chain with the history plugin.
• State history plugin exposes a websocket interface for something to connect to and read the block / state data from the additional new state history files stored in the data directory.
• There are 2 examples of state history websocket clients on the eosio GitHub:
  • C++: https://github.com/EOSIO/fill-postgresql
  • JavaScript: https://github.com/EOSIO/test-state-history

More advantages to the new flat file and websocket approach:

• Multiple fillers can connect to nodeos and read simultaneously from different locations in the flat file.
• When you need to rebuild your application state nodeos doesn’t need to be replayed as you’re reading from external files now.